Roadway markers are mounted on the surface of a roadway, along centerlines, edge lines, to delineate lanes for vehicular traffic.
Examples of commonly used retro-reflective pavement markers using a shell like housing filled with structural polymeric filler material are based on Heenan U.S. Pat. No. 3,332,327, Balint U.S. Pat. No. 3,409,344, or Hedgewick U.S. Pat. No. 5,002,424.
This type of markers are made of three to four steps or processes:
Firstly, injection molding a thermoplastic housing (shell), integrally molded with one or two reflective faces, the shell coated with a reflective metallic sealer by a process known as vacuum metalizing, the shell is then filled with a resinous filler material encapsulating the metalized cube corner reflective elements, thereby provide the marker the impact resistance structural body. This type of markers worked well for several months; however, due to sharp exterior geometric edge configuration and the incompatibility of the material composition for forming this type of markers with potted shell, often causes pealing and chipping of the reflective faces, thereby losing retro-reflectivity. Several method of applying abrasion resistant coating has been used to improve such pavement markers.
Other major development in the pavement marker art has been made; this was achieved by eliminating the use of the metalized sealer for the cube corner reflective elements. This applicant's U.S. Pat. No. 4,726,706, which is incorporated herein by reference in its entirety, divide the inside surfaces of the reflective faces into reflective cells, each cell having multiple cube corner reflective elements, the cells isolated from each other by partition and load carrying walls. The inside surfaces of the reflective faces are sealed with a thin polymeric sheet. Other prior art pavement markers have been designed attempting to reduce oncoming tire impact, attain better daytime visibility by incorporating luminescence color dyes or pigmentations. U.S. Pat. No. 5,667,335 to Khieu discloses a pavement marker comprises of three distinct parts, a base part with structural walls defining hollow cavities, a fiber reinforced shell having two inclined faces with at least one face having raised energy directors within a recessed area and at least one reflective lens plate having cube corner reflective elements.
U.S. Pat. No. 6,102,612 to Pricone discloses a sun country pavement marker 105 comprises a body member 110, a top member 130, and one or two reflective lens plates 192 agglutinated within designated recesses. In order to form hollowed body member 110, the top surface is open defining the hollowed body, which is sonically sealed with the additional third member 130 to complete a unitary structural body.
Several prior arts attempted to utilize a unitary structural body for reflective pavement marker fabrication. For example, U.S. Pat. No. 5,392,728 to Spear et al discloses an extruded one piece body with constant cross section having abrupt vertical sides which can be strongly felt during tire impact.
U.S. Pat. No. 4,875,798 to May et al discloses a pavement marker having one piece rigid body supported with partitions walls forming multiple hollow cavities which are open at the base surface. These open cavities at the base eliminated considerable bonding base surface parameter, thereby reduced the bond to the roadway surface.
U.S. Pat. No. 6,109,821 to Montalbano discloses a pavement marker with one piece solid body made of a closed cell foam thermoplastic. This type of material has limited durability due to the air entrapment for creating a low density solid plastic body.
The use of monolithically formed one piece hollowed structural body integrally containing multiple load carrying walls with wedge shaped top ends was disclosed by this Applicant's U.S. Pat. No. 6,267,530, No. 6,334,734 and U.S. Pat. No. 6,579,036. Although the wedged shape top surfaces of the load carrying walls within the recessed area of the front and back faces of the structural body of '036 was deemed to be sufficient for directly welding the reflective lens plate. However, there was no recognition apparent from the '530, 734 or '036 patents that the energy directors at top of each partition wall defining the reflective cells within the lens plate need to land and subsequently welded to a flat region on top of each wedge shaped top regions of the partition walls within the recessed faces of the structural body.
Also, there was no recognition apparent from the '530, '734 or '036 patents that the base surface of the structural body can integrally incorporate two types of grooves, a recessed deep grooves (cavities) within the center portion of the base region to reduce the polymeric material used to form the marker body and multiple slightly protruded grooves beneath the front, sides and back faces of the marker body. It has been found that by integrally incorporating at least one recessed V-shaped channel within the base surface will improve agglutination by reducing air bubble entrapment during agglutination of the marker base to a substrate, acting as air bleeding channel. The present invention's raised pavement marker with tilted, multi angular sides attain better daytime visibility by exposing larger non-reflective exterior surfaces areas to the vehicular traffic. Such frontal non-reflective surfaces within the marker body of the present invention are especially effective when incorporating fluorescent colorant dyes such as (thioxanthene) compounds, phosphorescent pigments such as (Strontium) and other luminescent dyes manufactured by pigment and dye manufacturers such as BASF, Day Glo Inc, American Dye Source Inc. Ciba-Geigy Corporation and others. Such colorants are added to the polymeric matrix as a blend to provide luminance yellow, orange, red or other colorant appearance for improving day time appearance and night time fluorescent visibility.
An example of such readily available fluorescent dye blends are D-191 and D-098 (yellow), D-063 and D-315 (orange) which are manufactured by Day-Glo Inc.
There is a continuous development of new and improved fluorescent colorants by several dye and pigment manufacturers. Some have developed new proprietary phosphorescent pigment that can glows for hours. By incorporating (Strontium), an earth alkaline, a self-emitting light technology allows an after glow time to exceed 12 hours which make it to be ideal luminous pigment for traffic safety applications. Many of these proprietary dyes chemistry are based on compounds that include (Thioxanthene) dyes.
These types of dyes are readily available in the market place as proprietary owned by others. Incorporating luminescent materials within traffic marking objects is a well known art. Several prior arts have utilized fluorescent colorants for traffic and pavement marking devices. As an example, U.S. Pat. No. 3,592,777 assigned to Owens-Illinois; U.S. Pat. No. 3,830,682 to William Rowland; U.S. Pat. No. 3,908,055 to Susuki et al; U.S. Pat. No. 4,208,300 to Phillippe Gravisse and U.S. Pat. No. 5,213,711 to Fast et al.
This invention also provides an alternative method of monolithically injection molding the unitary structural body in situ about one or two lens plate structures.
The lens plate structures utilized to form a reflective pavement marker in accordance to the present invention may be either simultaneously formed within the same rotary mold used in a two color (or two materials) injection molding machine, in one or two rotational steps. Alternatively, the lens Plates are pre-formed and inserted within a defined portion of a mold used to form the unitary body in a one-color injection molding machine. Both, the pre-insertion process (using a one-color injection molding machine) or simultaneously forming the transparent lens plates and the unitary body in a two-color injection molding machine allows the molding of the unitary marker body in situ about one or two lens plate means. These processes can be used to provide cavity means within the unitary structural body for pre insertion of other devices, such as luminance tube with LED as power source that may be used for light emitting or flashing light control means. Some devices may be controlled via light control information or programs stored in device memory and/or transmitted or downloaded to the devices. Devices also may include sensors so that the generated light may change in response to various operating or a user input.
This invention's unitary marker body can also be provided with means to embed photovoltaic cells within the top planar surface and utilized as a rechargeable power source for LED.
The goal of this invention is to have a highly versatile process for making a durable raised reflective pavement marker with high daytime and nighttime visibility and reflectance, low cost and can incorporate fluorescent dyes for light glowing or flashing effects which is utilizing the monolithically formed one piece structural body.
It has been found that incorporating one row of hollow cavities with variable depth on each side of the lens plates and open within the base surface will act as a shock absorber when vehicular tire impact the outer side of these hollow cavities, thereby minimize deflection caused by the impact stresses which may lead to lens plates dislodgement from the recessed face regions of the body.